Central to the operation of any internal combustion engine are three components: the working volume, the power transmission, and the timing mechanisms. The working volume of a reciprocating piston engine is created by a cylindrical chamber capped at one end by the head and at the other end by a movable piston. The power of expanding gas forces the piston down and is transmitted to offset journals on the crankshaft through a connecting rod. The timing is controlled by the position of the offset journals on the crank and by a cam operated poppet valve assembly in the head.
History has proven that there is an intense and timeless desire to improve the internal combustion (IC) engine. Improving fuel efficiency, power density, cost, and/or durability would be very appealing to any IC engine user. Improving most of these attributes without degrading others would be a dramatic advance in engine technology. Each year hundreds of attempts and millions of dollars are poured into making small improvements to the IC engine. Designers continue, however, to spend money looking for the one elusive key that will unlock a major advance in engine technology.
Over the years the rotary engine has been especially attractive in this search for a dramatic technological advance because of its demonstrated ability to deliver power in a small package. One of the primary advantages of the rotary engine is the simplicity of the mechanism that defines the working volume, power transmission and timing mechanisms. The simplicity of design not only reduces the number of moving parts, therefore increasing reliability, but the more efficient packaging reduces the outside envelope of an engine of given displacement.
The Wankel engine designed throughout the late 1930's and early 1940's by Felix Wankel and sold commercially by a number of companies, including Mazda Motor Company, is currently the most well known rotary engine. This engine proved popular even though it had several problems, including high hydrocarbon emissions, contributed to by such factors as rotor sealing, lubrication and port configuration, only a single power pulse per revolution per stage, and poor fuel economy. But, more importantly, this engine showed that the rotary engine could successfully be used in a mass-produced automotive market if appropriate attention, time and money are spent to develop the technology.
While the Wankel is the most well known rotary engine, it is by far not the only rotary engine known in the prior art. Many rotary engines have been patented in the past, including U.S. Pat. No. 1,298,839 to Weed; U.S. Pat. No. 2,050,603 to Gardner; U.S. Pat. No. 2,734,489 to Tschudi; U.S. Pat. No. 3,824,963 to Eda; U.S. Pat. No. 3,854,457 to Taurozzi; U.S. Pat. No. 4,194,871 to Studenroth; U.S. Pat. No. 5,326,238 to Schukey and U.S. Pat. No. 4,604,909 to Marson.
The thing that all of these engines have in common is the "rotating piston" design. All of these engines use a set of rotors that move within an annular volume. The difference between these prior art engines is primarily in the design the linkage that transmits the power and timing the engine. The Tschudi Engine, for example, uses a modified Geneva mechanism to move the pistons around the volume in alternating steps. This results in an engine that takes two revolutions to complete a power cycle (i.e., transmit a power pulse to each piston), giving it a power density similar to a reciprocating piston engine. Still other prior art engines took advantage of the fact that a mechanism could be created that allowed the engine to complete one power cycle per chamber every revolution. This increased the potential power density in the engine, but the fragile mechanisms used for timing these engines led to their downfall. All of these engines were susceptible to various failure modes.
Therefore, the various prior art rotary engine designs indicate that the rotary engine concept has the potential to outperform reciprocating piston engines in most respects if a more practical design can be developed. The present invention is directed toward meeting this need.